Study: 2,400 great white sharks prowl off California coast

The number of great white sharks in the Pacific Ocean has grown to 2,400, a study found. (Al Giddings — California Academy of Sciences)

The number of great white sharks that prowl the waters off Tomales Point, Stinson Beach, Duxbury Reef and Bolinas for marine mammals is larger than previously thought, according to a new study.

Some studies showed the population roaming in a section of sea from the Monterey Bay, Farallon Islands, north of Marin to Bodega Bay at between 200 and 400. That prompted calls for protection under the federal Endangered Species Act.

But the new effort published in PLOS ONE last month suggests that great whites -- also known just as white sharks -- are returning to abundance in the Pacific Ocean and puts the number closer to 2,400.

The study by a 10-member team led by George H. Burgess, director of the Florida Program for Shark Research, bolsters a recent National Oceanic and Atmospheric Administration determination that the eastern Pacific Ocean population of great white sharks does not warrant listing under the Endangered Species Act. The California Department of Fish and Wildlife Commission also made the same determination.

Under California law that went into place in 1994, it is illegal to take great white sharks whether it's sports fishing or commercially.

"That we found these sharks are doing OK, better than OK, is a real positive in light of the fact that other shark populations are not necessarily doing as well," Burgess said. "We hope others can take our results and use them as a positive starting point for additional investigation."

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Renowned shark expert and Mill Valley resident John McCosker he believes the numbers in the new study are accurate.

"They used more reliable techniques, and that there are on the order of at least 2,400 is good news. I don't believe they are at risk," he said. "And if you are a kayaker, paddler, surfer or swimmer there is no reason to be nervous, the number of attacks has not increased."

What has increased is attacks on otters and seals, McCosker noted, which means they are doing their job: keeping nature in balance.

White sharks continue to be a mystery, and there movements are not easily tracked, helping lead to the varying population estimates. While white sharks live for decades, they are not believed to reproduce rapidly. Male white sharks become sexually mature at around 10 years old, with females becoming mature at around 15 years. They can have between two and 14 pups per litter with the gestation period lasting about 12 months. Each pup is about 5 feet long at birth with a full set of teeth. They can grow up to 21 feet in length, according to state scientists.

Adult sharks feed on fish, seals, sea lions, dolphins, scavenged whale blubber, seabirds, turtles, rays as well as other sharks, according to state fish and wildlife scientists.

The county has been one of the prime spots for great white shark attacks over the years; 12 people have been attacked off the Marin coast, the most in the state. San Mateo and Monterey have seen 11 attacks, Sonoma and San Diego nine. Of the 101 recorded attacks in the state, 13 have been fatal.

Sharks do not target humans, but they do confuse people with other prey such as seals, experts say. Typically, if a shark bites into a human it will release the person, realizing the mistake. But the powerful physiology of the adult beast -- between 1,500 and 4,000 pounds and razor-sharp serrated teeth -- is sometimes enough to doom a human with one bite.

Sharks tend to be active closer shore from August through October, McCosker said, and they can sometimes be seen in the waters off places like Stinson Beach.

"That's the peak season of the salmon swimming down the coast, north to south," he said. "The pinnipeds are following the salmon and the sharks follow the pinnipeds."